原式=（2001*0.1+2001*0.01+2001*0.001+2001*0.0001）÷0.1111
=2001*（0.1+0.01+0.001+0.0001）÷0.1111
=2001*0.1111÷0.1111
=2001*（0.1111÷0.1111）
=2001